Ligação covalente normal [Módulo 04 - Aula 03]

Summary

This lesson covers covalent bonds, specifically normal covalent bonds, where electrons are shared between atoms. The video explains the fundamental concept of covalent bonding, where atoms like hydrogen share their electrons to achieve stability. It introduces key characteristics of covalent bonds, such as low melting and boiling points, and provides examples like water and carbon dioxide. The video also touches on the formation of molecular structures, bond types (sigma and pi), and how to determine formulas for covalent compounds. The lesson is concluded with exercises to apply the learned concepts.

Takeaways

• 😀 Covalent bonds are formed through the sharing of electrons between atoms, with no atoms gaining or losing electrons.
• 😀 A covalent bond is illustrated with the example of two hydrogen atoms sharing electrons to form H2.
• 😀 Compounds with covalent bonds are called molecular compounds, which have low melting and boiling points.
• 😀 Molecular compounds can exist in different states (solid, liquid, gas) depending on the substance (e.g., sugar, water, CO2).
• 😀 Covalent bonds can occur between nonmetals or between a metal and hydrogen, such as in the hydrogen molecule (H2).
• 😀 In a covalent bond, each atom contributes one electron to form a shared pair, ensuring stability in the molecule.
• 😀 Covalent bonds can be single, double, or triple, with single bonds being the strongest (sigma bonds).
• 😀 The type of covalent bond (sigma or pi) depends on the number of bonds: one sigma bond for single, and pi bonds for double or triple bonds.
• 😀 The Lewis structure is used to represent the electron configuration and bonding in molecules, with lines representing shared pairs of electrons.
• 😀 The octet rule is essential for determining the stability of molecules, and the atom that needs more electrons to complete its octet usually becomes the central atom in a molecule.
• 😀 To write the electronic structure of molecules like methane (CH4), you distribute electrons based on the number of valence electrons, ensuring each atom reaches stability (octet for non-hydrogen atoms and duet for hydrogen).

Q & A

What defines a covalent bond?

A covalent bond is characterized by the sharing of electrons between two atoms, where neither atom gains or loses electrons. Both atoms use the electrons together, forming a stable bond.

Can you give an example of a covalent bond formation?

An example is the bond between two hydrogen atoms. Each hydrogen atom has one electron, and these two electrons are shared between the two atoms, forming a covalent bond.

What are the characteristics of compounds with covalent bonds?

Compounds with covalent bonds, known as molecular compounds, typically have low melting and boiling points. They can exist in solid, liquid, or gas form at room temperature, such as sugar (solid), water (liquid), and CO2 (gas).

What are the types of atoms that form covalent bonds?

Covalent bonds usually form between nonmetals or between a metal and hydrogen. A specific example is hydrogen bonding with itself.

What is a normal covalent bond?

A normal covalent bond is formed when each atom contributes one electron to create a shared pair. For example, in a hydrogen molecule (H2), one electron from each hydrogen atom is shared.

What is the difference between sigma and pi bonds?

A sigma bond is the strongest type of covalent bond and occurs in a simple, single bond. A pi bond is weaker and occurs in double or triple bonds, alongside a sigma bond.

How do you determine the central atom in a molecular structure?

The central atom in a molecular structure is usually the atom that needs more electrons to complete its octet. For example, in methane (CH4), carbon is the central atom because it requires four electrons to complete its octet, while hydrogen only requires two electrons.

How do you build an electronic structure for a molecule like methane (CH4)?

To build the electronic structure of methane, you sum up the valence electrons of each atom, then distribute them as pairs between the atoms, ensuring each atom satisfies its valency rule, with carbon in the center and hydrogen around it.

What is the significance of Lewis structures in understanding covalent bonds?

Lewis structures visually represent the bonding between atoms and the distribution of electrons. They help us understand the sharing of electrons in covalent bonds and identify non-bonding electron pairs.

How would you classify the bonds in a molecule like methane (CH4)?

In methane, all the bonds between carbon and hydrogen are sigma bonds, as it consists of single bonds formed by the sharing of electrons between carbon and hydrogen atoms.